1. Field of the Invention
The present invention relates to a fiber connecting method for combining a plurality of laser beams by bundling a plurality of fibers and connecting them to a single-core fiber, and a laser apparatus and a projection television using the method.
2. Description of the Related Art
The conventional method of connection employed in the field of a pumping semiconductor laser of a solid laser using an optical fiber bundle will be explained. In Jpn. Pat. Appln. KOKAI Publication No. 2001-15839, an “optical fiber pumping solid laser apparatus” is disclosed, in which a laser beam generator having a high pumping efficiency is obtained by connecting an optical fiber bundle with a plurality of fiber output semiconductor lasers and a single-core optical fiber to each other. The advantages described in this publication are that a high connecting efficiency can be achieved by combining the size of the outer periphery of the core of the fiber bundle and the core diameter of the single-core fiber and that the use of a single-core can suppress the irregularities of the laser beams emitted from the cores of the fiber bundle.
This prior art is based on a prerequisite that the laser beams from the fiber bundle have the same characteristics, and therefore intended to mix a plurality of laser beams to some degree and thereby obtaining a uniform output as a whole.
When the laser beams from the fiber bundle have different characteristics or, for example, have different wavelengths, however, the laser beams from the fibers are required to mix with each other uniformly.
Normally, a laser beam is propagated through a fiber in any of predetermined several mode patterns unique to each fiber. The laser beam entering a fiber propagates through the fiber by being connected with a mode pattern capable of propagation. Frequently, however, the laser beam propagates in a mode pattern first connected. Therefore, the difference of the incidence point is directly reflected in the difference of the connecting mode pattern. This poses the problem that the exit pattern from the single-core fiber is varied from one wavelength to another depending on the point of incidence. The problem is especially serious in an application of a display for obtaining white light.
Specifically, when a fiber bundle and a single-core fiber are connected with each other, the exit pattern from the single-core fiber is varied with the position of each fiber in the fiber bundle. Thus irregularities are caused, thereby posing the problem that it is impossible to obtain an exit light having a uniform mixture of laser beams.